Weighing utensil

ABSTRACT

A utensil ( 1 ) for weighing a sample ( 6 ) has fill ( 2 ) and discharge ( 3 ) positions. The utensil has a receptacle ( 4 ) with an attached neck ( 5 ). An outside surface ( 7 ) of the receptacle has a seating surface ( 9 ) that defines a plane, as well as a fill opening ( 13 ), through which the sample is placed when the utensil is in the fill position. A passage opening ( 15 ) and a discharge opening ( 14 ), at the ends of the neck, allow sample flow from the receptacle through and out of the neck when in the discharge position, with flow into the neck occurring between the fill and discharge positions. The neck has at least one support contact point in the plane of the seating surface, so that the receptacle rests on both the seating surface and the at least one support contact point when in the fill position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is entitled to benefit of a right of priority under 35 USC §119 from European patent application 12173020.4, filed 21 Jun. 2012, the content of which is incorporated by reference as if fully recited herein.

TECHNICAL FIELD

The present invention concerns a weighing utensil that serves to weigh a substance or to transfer a substance into a volumetric flask or another type of receptacle used in the laboratory for the preparation of solutions. In the fill position of the weighing utensil, a substance is put into the latter, and the weighing utensil with the substance is weighed. In the discharge position of the weighing utensil, the substance can be transferred into the volumetric flask.

BACKGROUND

Typically, weighing utensils of this kind are used in the laboratory for the preparation of solutions.

Solutions are typically mixtures of at least one liquid and at least one solid substance that is dissolved in the at least one liquid. The concentration of a solution is the quantitative proportion of the solid substance relative to the at least one liquid in which it is dissolved. To ensure that a solution contains an accurate proportion of a dissolved substance, the respective quantities of the solution and of the substance have to be accurately measured. In the laboratory, the quantity of a solution is normally determined volumetrically, while the substance is weighed. A volume is normally measured by means of a volumetric flask. A volumetric flask is a specific type of bottle with a wide body and a long narrow neck. A graduation mark on the neck defines the given volume, for example 100 milliliters. The volumetric flask has a stopper which is inserted into the neck. The section of the neck that is in contact with the stopper is precision-ground and is referred to as a ground mouth of the flask. The ground mouth and the stopper together serve to provide a tight seal of the flask which minimizes the loss of solution for example when the flask is shaken.

The quantity of the solid substance, on the other hand, is determined by weighing, and it is therefore also referred to as the weighing sample. First, a receptacle is placed on a balance, whereupon the latter is tared, i.e. reset to zero. Next, the substance is incrementally added to the receptacle until the desired weight has been reached. When this so-called weighing-in process is completed, the receptacle is held over the volumetric flask and rinsed with the liquid by pressing the latter out of a squeeze bottle, so that the substance is washed completely into the volumetric flask. After the substance in its entirety has been transferred to the volumetric flask and dissolved in the liquid, and after the liquid has been topped off to the graduation mark and the mixture has been homogenized, a homogeneous solution has been obtained as a result.

Conventionally a paper weighing boat which is made of a sheet of parchment paper is used as receptacle. The sheet of parchment paper can be folded into a desired shape. Normally, the folding produces a receptacle with a bottom and deep sides. Paper weighing boats are a very handy means for holding and weighing the substance. Transferring the substance, on the other hand, proves to be more difficult. Due to the light weight and the pliability of the paper weighing boat, it takes diligence to manipulate it with skill and precision. In the process of dumping the substance into the measuring flask, the weighing boat can easily slip out of one's hands or be crushed.

It is also common to use weighing boats of a plastic material, for example polystyrene. They are available commercially in rectangular, rhombic or hexagonal shapes with a wide bottom and low, slanted sides. Due to their flat bottoms, they rest very securely on a flat surface for the filling and weighing of the substance. They have the advantage of being pliable, which makes it possible to channel the flow of the substance when transferring the latter into the measuring flask. However, like the paper weighing boats, the plastic boats are so light and soft that the substance can easily get spilled.

U.S. Pat. No. 6,179,022 discloses a receptacle in the shape of a weighing funnel which is made of plastic. Similar weighing funnels are also known which are made of glass. The weighing funnel consists of a receptacle with a fill opening for the substance. A neck with an opening for the discharge of the substance from the weighing funnel is connected to the receptacle. In one embodiment of the weighing funnel, the receptacle has a flat surface parallel to the axis of the neck, which makes it easier to place the substance in the receptacle. While transferring the substance into the measuring flask is safer with the weighing funnel than with the conventional weighing boats, the weighing funnel still has the disadvantage that it can roll over easily because the flat surface is not large enough, and/or it can lose its equilibrium because of the neck. Thus, the stable position of such weighing funnels during the filling and weighing operation cannot be assured.

A further disadvantage of the conventional weighing funnel is its short and narrow neck. Due to the narrow outside diameter of its neck, the weighing funnel does not sit securely in the neck of the measuring flask. The weighing funnel will be loose in the measuring flask. This makes the rinsing of the weighing funnel with a jet of liquid cumbersome and increases the risk of spills.

The shortness of the neck of the weighing funnel also leads to a loss of substance, as the substance flowing out of the weighing funnel into the measuring flask will come into contact with the ground surface at the mouth of the flask and a small part of the substance will necessarily remain there. Thus, substance particles will be caught between the ground mouth and the stopper and therefore not get dissolved in the subsequent shaking, resulting in an incorrect concentration.

It is critical for the accurate concentration of the solution that at the end of the procedure the entirety of the weighed substance is transferred into the liquid. Accordingly, no substance may remain in the receptacle or between the ground mouth of the flask and the stopper.

The present invention therefore has the objective to provide a weighing utensil which allows the substance to be weighed and transferred into a measuring flask with a minimal loss and which makes the handling as convenient and safe as possible.

SUMMARY

This task is solved with a device and a method having the characteristics specified in the independent patent claims. Further advantageous embodiments are described in the dependent claims.

The invention covers a weighing utensil with a receptacle and with a neck arranged on the receptacle, wherein in the fill position of the weighing utensil a substance can be filled into the receptacle, and in the discharge position of the weighing utensil the substance inside the receptacle can flow out through the neck. The receptacle has a flat seating surface arranged on the outside of the receptacle, and a fill opening through which a substance can be filled into the receptacle when the weighing utensil is in its fill position, i.e. the position in which the weighing utensil rests on its flat seating surface. At a first end of the neck there is a passage opening through which the substance can flow out of the receptacle when the utensil is in discharge position, and at a second end of the neck there is a discharge opening for the discharge of the substance from the neck when the utensil is in discharge position. The neck and the receptacle are connected to each other in such a way that between the fill position and the discharge position the substance can flow out of the receptacle by way of the passage opening and through the neck. The neck has at least one support contact point in the same plane as the seating surface of the receptacle, so that in the fill position of the weighing utensil, the latter will rest on the seating surface and on the at least one support contact point.

This arrangement is advantageous in that it allows the weighing utensil to rest securely on a flat surface, for example on a table or on a balance. Thus, the weighing utensil remains in a stable condition, supported at the seating surface and the support contact point, and there is no risk that it could tip over sideways or to the back. In addition, since the weighing utensil is thus on a stable footing, the operator has both hands free for the filling of the weighing utensil. The weighing sample can be an expensive, dangerous, or even toxic substance. Therefore, care needs to be taken already in the filling of the weighing utensil in order to minimize spillage and/or to prevent the substance from getting into contact with the skin of the operator.

A weighing utensil according to a particularly preferred embodiment has not only a support contact point but a support contact surface on the neck extending in the same plane as the seating surface of the receptacle. This embodiment has the advantage that it is even more stable. The support contact surface on the neck is ideally arranged in such a way that the width of the discharge opening is reduced as little as possible.

The seating surface is preferably arranged so that the longitudinal axis of the neck is inclined at an acute angle to the plane of the seating surface. With the neck at an acute angle to the seating surface, the rinsing liquid can reach the inside bottom of the receptacle more easily when the weighing utensil is in discharge position. In weighing utensils of the existing state of the art, the seating surface and the neck are aligned parallel to each other. This means that in the discharge position the seating surface of the receptacle is oriented vertically. Due to the small angle between the bent-over neck of a squeeze bottle and the receptacle bottom on the inside of the seating surface, the weighing utensil cannot be rinsed out efficiently. The ideal angle for effective rinsing is between 20° and 40°, so that the inside bottom of the weighing utensil is sprayed at an angle of about 60° to 90°, which allows a direct, convenient and efficient flushing of the weighing utensil.

In an advantageous embodiment of the invention, the tangential planes at all points of the surface of the weighing utensil are inclined relative to the axis of the neck at angles of the same algebraic sign or at an angle of zero degrees. In other words, the tangential planes at all points of the surface of the weighing utensil cross the axis of the neck in the same direction or are parallel to the axis of the neck. Accordingly, the shape of the weighing utensil is free of projections that would prevent its release from a single-piece casting mold. This property allows the weighing utensil to be manufactured by injection molding, using a mold without transverse slide. Thus, the casting can be taken out of the mold quickly and easily without subjecting the weighing utensil to bending. In addition, it makes the manufacturing process more efficient and thus more economical.

It is of particular advantage that the receptacle is significantly wider than the neck. Ideally, the receptacle is twice as wide as the neck is at its widest diameter. This proportion promotes a good and comfortable grip on the weighing utensil for the filling as well as the rinsing.

It has been found to be beneficial to design the fill opening with the same width as the receptacle. With the weighing utensil in fill position, the user thus has a clear space to hold his implements above the receptacle bottom when placing the substance into the weighing utensil. In addition, this kind of fill opening facilitates the rinsing of the weighing utensil in the discharge position.

The receptacle has an inside surface which, in an advantageous embodiment, includes a bottom area where the weighing substance can be placed. The bottom area is located essentially opposite the seating surface of the receptacle. The bottom area is surrounded by a peripheral surface zone that is inclined at obtuse angles to the bottom area, ideally between 100° and 140°. In this arrangement, it is particularly advantageous that the receptacle has the shape of a wide and open bowl. Thus, the weighing utensil can be rinsed easily in the discharge position. The liquid jet of the squeeze bottle can reach the bottom area and the peripheral zone without a problem. Also, it is practically unnecessary to tilt the squeeze bottle in order to aim the liquid jet directly, i.e. with an incident angle of about 90°, at the bottom area and the peripheral zone.

Furthermore, the receptacle and the passage opening can be designed so that the threshold of the passage opening is at a height A above the level of the bottom area. In the fill position the substance can therefore not flow out of the receptacle through the neck. This feature is particularly advantageous for liquid substances as it reduces the risk that substance may get lost in the change from the fill position to the discharge position.

In a further embodiment of the weighing utensil, the fill opening is designed so that the vertical projection of the fill opening overlaps the bottom area. This feature offers the user an unobstructed view of his manipulations. In addition, it allows him to place the substance on the bottom area from above.

The aforementioned features contribute to limiting the loss of substance during the filling and weighing operations. Also, when transferring substance from the weighing utensil to the measuring flask, there is a risk of losing some of the substance. For example, portions of the substance that come into contact with the ground glass surface at the mouth of the flask will not be washed away by the solution after the stopper has been put in the flask.

The discharge opening is therefore preferably at a lower level than the ground glass area when the weighing utensil is seated in a measuring flask with a ground neck. Thus the outflowing substance will not come into contact with the ground glass surface.

The neck of the weighing utensil can be shaped conically and/or cylindrically. There can be one or more sections of decreasing diameter, i.e. the neck does not need to have a continuous taper. It can have conical and/or cylindrical sections.

According to the German industry standard DIN 12664, the ground glass mouth of a measuring flask has a 1:10 taper. It is therefore especially advantageous to design the weighing utensil with a conical neck that has a taper of 1:10, so that in the discharge position the neck will conform to the ground glass surface.

In a further advantageous embodiment of the invention, the neck of the weighing utensil has at least two sections with a 1:10 taper. The sections have different diameters and are connected by more strongly tapered transitions. Due to the transitions, the length of the neck is limited. A weighing utensil with this kind of neck can be set into measuring flasks with different mouth sizes. When the weighing utensil is in discharge position on a wide measuring flask with a large diameter, the neck of the weighing utensil does not come into contact with the liquid inside the measuring flask.

The weighing utensil can further be equipped with a handle. The handle is preferably arranged at the receptacle, for example at the opposite end from the discharge opening.

Beside the weighing utensil, the scope of the invention extends to a method according to which a substance is filled into a weighing utensil that is set up in a fill position, wherein the weighing utensil is subsequently seated upright in a discharge position in the opening of a measuring flask so that the substance flows out into the measuring flask.

The receptacle can have a fill opening with a rounded contour at the opposite end from the discharge opening. Such a design has the advantage of a larger inside surface of the receptacle and/or a larger bottom area.

The receptacle can also have a fill opening with a pointed contour at the opposite end of the discharge opening.

For pulverous substances, a weighing utensil with a biased discharge opening is particularly suitable. For liquid substances on the other hand, a weighing utensil with a discharge opening perpendicular to the axis of the neck is used.

The weighing utensil can be made of glass. However, disposable weighing utensils are made mostly of plastic, typically of polypropylene, polyethylene and/or polystyrene.

The loss of substance can also be reduced by making the weighing utensil of an anti-static material.

BRIEF DESCRIPTION OF THE DRAWINGS

The weighing utensil and the method of filling a substance into a measuring flask are hereinafter described through examples which are illustrated schematically in the drawings, wherein identical parts are identified by identical part numbers and wherein:

FIG. 1 is a side sectional view of the weighing utensil in fill position in a drawing plane that contains the axis of the neck and is perpendicular to the plane of the seating surface of the receptacle;

FIG. 2 is a top plan view of the FIG. 1 weighing utensil in fill position;

FIG. 3 is a perspective view of the FIG. 1 weighing utensil in fill position;

FIG. 4 is a side view of the FIG. 1 weighing utensil in discharge position, seated in the neck of a measuring flask;

FIG. 5 shows the FIG. 1 weighing utensil seated in discharge position in a measuring flask, in the process of being rinsed with a squeeze bottle; and

FIG. 6 is a top view of a second embodiment of the weighing utensil with a handle.

DETAILED DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 3 show, in side sectional, top plan and perspective views, a weighing utensil 1 in its fill position 2. The two main parts of the weighing utensil 1 are made evident, i.e., the receptacle 4 and the neck 5. The receptacle 4 has the shape of a bowl with an inside surface 8 and an outside surface 7. The outside surface 7 of the receptacle includes a seating surface 9. The seating surface 9 is flat and serves to put the weighing utensil on a flat base for example on a table or on a balance. The inside surface 8 consists of a flat bottom 16 and of a peripheral zone 17 surrounding the flat bottom 16. In the sectional plane of FIG. 1, the peripheral zone 17 rises up from the flat bottom 16 at angles β and γ, which are obtuse angles, i.e. larger than 90°. In this configuration, the flat bottom 16 and the peripheral zone 17 form an open inside surface 8 of the receptacle. This facilitates the rinsing out of the substance 6. The bottom is located essentially at the center of the receptacle 4. It is essentially flat and can be in parallel alignment with the support contact surface 9. A weighing sample 6 such as for example a chemical or biological substance is put by the user into the receptacle 4. The weighing sample 6 is brought in through a fill opening 13 and placed on the bottom area 16.

The receptacle 4 is connected to the neck 5. The latter has at one end a passage opening 15 through which the weighing substance 6 can flow out of the receptacle 4 when the weighing utensil is the discharge position 3. At the other end of the neck 5, there is a discharge opening 14 through which the weighing substance 6 leaves the weighing utensil 1. The neck 5 has three conical sections 19 that have a 1:10 taper. This is also the conicity of the ground-glass surface 22 inside the mouth of the measuring flask 21. Thus, the neck 5 sits securely against the ground-glass surface 22 in the opening of the measuring flask 21 which provides a stable support. The plurality of sections 19 of the neck 5 serve the purpose that the weighing utensil can be used for measuring flasks with different opening diameters. With the more strongly tapered transitions 20 between the sections 19, a larger range of diameters can be covered with a limited length of the neck 5.

The receptacle 4 connects to the passage opening 15 of the neck 5. The axis 12 of the neck 5 is slanted downward towards the discharge opening at an angle α relative to the plane of the seating surface 9. In other words, the axis 12 of the neck 5 and the seating surface 9 of the receptacle 4 are not parallel to each other. When the utensil is in the fill position 2, the neck 5 rests on a support contact surface 10 and contributes to the stability of the weighing utensil 1. The threshold of the passage opening 15 of the neck 5 is elevated at a height A above the level of the bottom area 16. Thus, the weighing substance 6 cannot flow out through the neck 5 when the utensil is in the fill position 2.

Directing attention now to FIG. 2, the top plan view shows that the fill opening 13 has essentially the same width as the receptacle 4. The bottom area 16 and the peripheral zone 17 appear in the middle of the fill opening 13. The width E of the bottom area 16 is approximately half as large as the width B of the fill opening 13. The size of the fill opening 13 and its centered position relative to the bottom area 16 show that the user can place the weighing substance on the bottom area 16 in an easy manual operation using laboratory implements such as a spoon, tweezers, a dissecting needle or a spatula.

The perspective view of FIG. 3 shows a weighing sample 6 that has been placed on the bottom area 16 of the weighing utensil 1.

FIG. 4 a illustrates a weighing utensil 1 in discharge position 3. The neck of the weighing utensil 1 is seated in the neck of a measuring flask 21. The taper of the sections 19 of the neck 5 is equal to the conicity of the ground-glass surface 22, i.e. 1:10, so that the neck 5 is in form-fitting engagement with the ground-glass mouth 22 of the flask 21. The discharge opening 14 is at a lower level than the ground-glass surface 22; consequently the weighing substance 6 flows out into the measuring flask 21 without coming into contact with the ground-glass surface 22.

FIG. 4 b represents an enlarged view of the ground-glass mouth portion 22 of a measuring flask 21. While the neck 25 of the measuring flask 21 is cylindrical, the ground-glass portion 22 is tapered with a conicity of 1:10 in accordance with DIN 12664.

In a perspective view, FIG. 5 illustrates the FIG. 1 weighing utensil 1 in discharge position 3, seated in the neck of a measuring flask 21. A weighing substance 6 on the bottom area 16 of the weighing utensil 1 flows, propelled by its own weight, into the neck 5 of the weighing utensil 1. A squeeze bottle 24, which stands to the left of the measuring flask 21, is used to spray a jet of liquid onto the weighing substance 6. In this way, the inside 8 of the receptacle and especially the bottom area 16 of the weighing utensil 1 are rinsed off. The weighing substance 6 attacked by the spray jet flows with the liquid through the neck 5 of the weighing utensil 1 into the measuring flask 21. This procedure is carried out in such a way as to minimize the residues of the weighing substance 6 remaining in the weighing utensil 1 and to maximize the amount of weighing substance 6 that flows into the measuring flask 21. As is apparent from this drawing, a bottom area 16 that is slanted slightly backwards can be rinsed effectively with the squeeze bottle 24. The liquid jet ideally meets the bottom are 16 of the weighing utensil 1 at an angle of 70° to 90°. The large width B of the fill opening 13 as well as the obtuse angles β and γ of the peripheral zone 17 allow a good exposure of the bottom area 16 and the peripheral zone 17 to the liquid jet and thus ensure that only minimal residues of the weighing substance 6 remain in the weighing utensil 1.

As is apparent from FIGS. 1, 2 and 4 showing, respectively, a sectional view, a top view and a side view, the tangential planes at all points of the surface of the weighing utensil 1 are inclined relative to the axis of the neck at angles of the same algebraic sign. Consequently, the weighing utensil can be manufactured by injection molding using a single-piece mold, and the casting can be taken out of the mold without subjecting the weighing utensil to bending.

FIG. 6 illustrates a further weighing utensil 1 according to the invention which has a handle 23. The handle 23 is formed as an extension of the receptacle 4 at the opposite side of the discharge opening 14. The handle 23 allows the user to hold the weighing utensil without covering up the contents with his hand. Thus the user can keep the weighing substance 6 in view while handling the weighing utensil 1, for example to move it from the table to the balance and from the balance to the measuring flask 21. Furthermore, a large handle 23 can be grasped more comfortably and reduces the risk of coming into contact with the substance, which is especially important when handling toxic substances.

Although the invention has been described through the presentation of specific examples of embodiments, it will be evident to the reader that numerous further variant embodiments could be developed from the teachings of the present invention, for example by combining the features of the individual examples with each other and/or by interchanging individual functional units between the embodiments described herein. 

What is claimed is:
 1. A utensil for receiving and weighing a sample substance when the utensil is positioned in a fill position and for discharging the sample substance into a measuring flask having a flask neck with a standardized ground glass mouth at an end thereof when the utensil is positioned in a discharge position, the utensil comprising: a receptacle with a fill opening and a seating surface provided on an outside surface thereof, the seating surface defining a plane, and positioned relative to the fill opening so that the sample substance is placed into the receptacle while the utensil is in the fill position, with the utensil resting upon the seating surface; and a utensil neck, arranged on the receptacle, with a passage opening at a first end thereof, communicating the receptacle to the utensil neck and a discharge opening at a second end thereof, the utensil neck and discharge opening sized and adapted so that, when the utensil neck is seated into the ground glass mouth in the discharge position, the discharge opening extends into the flask neck beyond the ground glass mouth; the utensil neck having at least one support contact point, located in the plane of the seating surface so that, in the fill position, the utensil rests on both the seating surface and the at least one support contact point.
 2. The utensil of claim 1, wherein: the at least one support contact point comprises a support contact surface defining a plane in the same plane as the seating surface, so that, in the fill position, the utensil rests on both the seating surface and the support contact surface.
 3. The utensil of claim 2, wherein: the utensil neck has an axis that is inclined at an acute angle to the plane of the seating surface.
 4. The utensil of claim 3, wherein: the receptacle and the utensil neck each have tangential planes at all points of the surface thereof which are inclined relative to the utensil neck axis at angles of the same algebraic sign or at an angle of zero degrees.
 5. The utensil of claim 1, wherein: the receptacle has a width that is significantly larger than wider than a width of the utensil neck.
 6. The utensil of claim 1, wherein: the fill opening has a width substantially equal to a width of the receptacle.
 7. The utensil of claim 1, wherein: the receptacle has an inside surface comprising a bottom area adapted to receive the sample substance, the bottom area surrounded by a peripheral surface zone that inclines away from the bottom area at at least one obtuse angle.
 8. The utensil of claim 7, wherein: the passage opening is connected to the receptacle a height above the level of the bottom area, so that, while in the fill position, the substance sample substance cannot flow out of the receptacle through the neck.
 9. The utensil of claim 7, wherein: when in the fill position, the fill opening projects vertically onto the plane of the seating surface to essentially overlap the bottom area.
 10. The utensil of claim 1, wherein: Along a length thereof, the utensil neck has at least one conical portion, tapering down at a rate of 1:10, so that the utensil neck conforms to the standardized ground-glass mouth when in the discharge position.
 11. The utensil of claim 10, wherein: the utensil neck has at least two conical portions, each having the 1:10 taper and a different diameter.
 12. The utensil of claim 1, wherein: the utensil neck comprises at least one region of decreasing diameter.
 13. The utensil of claim 1, further comprising: a handle adjoining the receptacle.
 14. The utensil of claim 1, wherein: the utensil neck has an axis that is inclined at an acute angle to the plane of the seating surface.
 15. The utensil of claim 14, wherein: the receptacle and the utensil neck each have tangential planes at all points of the surface thereof which are inclined relative to the utensil neck axis at angles of the same algebraic sign or at an angle of zero degrees.
 16. The utensil of claim 4, wherein: the receptacle has an inside surface comprising a bottom area adapted to receive the sample substance, the bottom area surrounded by a peripheral surface zone that inclines away from the bottom area at at least one obtuse angle.
 17. The utensil of claim 16, wherein: the passage opening is connected to the receptacle a height above the level of the bottom area, so that, while in the fill position, the substance sample substance cannot flow out of the receptacle through the neck.
 18. The utensil of claim 16, wherein: when in the fill position, the fill opening projects vertically onto the plane of the seating surface to essentially overlap the bottom area.
 19. A method for placing a sample substance into a measuring flask, comprising the steps of: placing the sample substance into a utensil according to claim 1, with the utensil arranged in the fill position thereof; and setting the weighing utensil upright in the discharge position thereof, with the utensil neck in the mouth of the measuring flask, so that the sample substance flows out into the measuring flask. 